20.Where should an object be placed from an converging lens of focal length 20cm,so as to obtain a real image of magnification 2?

Q. In order to obtain a real image of magnification 2 using a converging lens of focal length 20 cm, where should an object be placed

Q. Where should an object be placed from a converging lens of focal length $15cm$, so as to obtain, a real image of same size as that of the object?

Q.

A diverging lens, focal length $f_1=20\text{cm}$ is separated by 5 cm from a converging mirror, focal length $f_2=10\text{cm}$. Where should an object be placed from the lens so that a real image is formed at the object itself ?

Q. A diverting lens of focal length $20cm$ and converging mirror of focal length $10cm$ are placed coaxially at a separation of $5cm$. Where should an object be placed so that a real image is found at the object itself?

Q. A diverging lens of focal length 20 cm and a converging mirror of focal length 10 cm are placed coaxially at a separation of 5 cm. Where should an object be placed so that a real image is formed at the object itself?